Researchers have known that some lizards have green blood due to bile pigments:
In fact, six species of lizards found in New Guinea are known to have green blood. The levels of bile found in their blood are four times higher than the toxic level for humans.
New research shows that green blood evolved independently 4 times in evolutionary history. These findings suggest that high levels of circulating green bile must be advantageous to the animals. For humans, research suggests that green bile pigments might kill parasites like malaria. Thus, it is possible that these lizards evolved high levels of green bile pigments to fight parasites as well, although much more research would be needed to answer this question.